Communication system switches frequently deploy multifunction voice or voice-and-data terminals which generally require a complex multi-octet terminal protocol to drive the terminal interface and to control transport services. Such a multi-octet protocol is typically field oriented, and may include, e.g., a header field, a command pointer field, a command data field interpreted according to the contents of the command pointer, and an integrity check field. Each field is usually defined as a collection of one or more bits, and certain bits or collections of bits are dedicated to certain functions. This creates fixed relationships between bits and command interpretations. In addition, the deskset terminal design is such that a large number of bits are assigned or reserved for numerous feature keys and feature indicator controls. When such a system is upgraded to support wireless terminals, use of the existing wired terminal protocol is desirable from a switch software point of view, since re-use of the protocol is generally a low-cost implementation. Unfortunately, this conventional approach requires excessive bandwidth, and fails to optimize the control protocol for the wireless voice terminal.
There are a number of issues associated with use of an existing wired terminal protocol to support wireless terminals. For example, the wireless terminal by its very nature is designed to be small and easily portable. The direct consequence of this is that there is an extremely limited area on the terminal user interface for feature access presentation. This implies that the wireless terminal control protocol requires many fewer codepoints for feature button and associated feature indicator pairs. Further, the area for a switch-controlled display on the wireless unit may be much smaller, and therefore only a subset of the normative wired terminal display control functionality is required to support the wireless terminal. In addition, a significant portion of the information displayed by a wireless terminal relates to the condition of the terminal itself, e.g., battery charge remaining, signal strength, etc., and is not commanded by the switch. Conventional techniques for utilizing a wired terminal protocol to support wireless terminals have failed to adequately address these and other important issues, and as a result these techniques suffer from the above-noted problems of excessive bandwidth consumption and lack of optimization.
A need therefore exists for techniques which allow an existing wired terminal protocol to be custom-fit to a wireless terminal interface, in order to capitalize on the existing switch software codebase, to reduce the amount of bandwidth consumed for terminal control, and to preserve the functionality of the system as represented to the user via the wireless terminal.